Ice hockey sticks are well known in the art. They are usually made up of two parts: a straight elongated shaft, rectangular in cross-section and a blade mounted at the distal end, or heel, of the shaft. A reinforcing high modulus light weight fabric is wrapped under the blade and covers the two faces of the blade as well as the distal portion of the shaft.
The cross-sectional dimensions of the ice hockey shaft have not changed much over the years as they were governed originally by the necessity for the player to have a good grip on the shaft in particular to prevent undesired rotation of the shaft.
The four axial apex or corners of the hockey stick shaft are usually rounded in order to provide comfort for the hands of the player while maintaining a good grip thereon. The hockey stick shaft is advantageously uniform in cross-section along its length until about 11 inches (about 0.28 m) from the heel where there is a taper to provide a smooth engagement therewith.
The shaft has conventionally been made of solid heavy hardwoods such as, for example, white ash or birch. These hardwood shafts usually require no reinforcement. They are advantageously glued to a one piece blade of the same type of wood, the blade alone being reinforced with a single layer of light woven fibreglass fabric covering the under blade and the two wider faces of the blade on the outside.
Such conventional hockey stick made of white ash which has an average density of 0.65 grams per cubic centimeters will weight, on average, about 700 g.
Players are often looking for lighter weight hockey sticks that do not sacrifice the stiffness and the resistance of the shaft to breakage.
Since little can be done to reduce the weight of the blade which represent a small percentage of the total weigth of the hockey stick, the efforts to reduce the weight of the hockey stick are usually directed to the shaft.
Many techniques have been proposed to reduce the weight of the hockey stick shaft. For example, the application of unidirectional fibreglass resin thin strips glued or moulded directly along the two wide sides of the hockey shaft in association with the use of a solid low density wooden core, such as, for example, aspen allowed the reduction of the weight of the hockey stick. This technique is disclosed in Canadian Patent No 1,151,693 issued on Aug. 9, 1983 to Goupil et al. In this patent, the wooden core, which can be made of solid and relatively light hardwood such as Ramin, is reinforced with fibreglass. This hardwood is lighter and less expensive than the conventional northern white ash, or birch solid wood or laminated wood that is conventionally used. Another method consists in using a very light hardwood such as aspen or poplar for a solid core, reinforcing the two wider opposite surfaces with a layer of high modulus fibre such as glass and carbon fibres. It also comprises rigid binding resin which has resulted in the production of relatively light weight and stiff handle at low cost. This technique has been very popular on the markets for many years.
Another technique used to produce a lightweight but stiff shaft in a hockey stick, possessing a supporting axial core made of hardwood, is to provide one or more transversal or axial cavities in various shape, size and position relative to the outside surface of the shaft and then to reinforce the shaft with aircraft plywood, fibreglass or a combination of glass and carbon fibres. U.S. Pat. No. 5,879,250 issued to Tähtinen et al. on Mar. 9, 1999 describes such a reinforcement technique. This technique has the significant drawback that since the cavities are open to the external surface of the wooden portion of the shaft, it weakens the shaft and it allows the adhesive used to secure the reinforcement to enter the cavities and to reduce the efficiency of the weight reduction.
One interesting development that proposes to design a hockey stick provided with a hollow central cavity surrounded by various types of medium and high costs plywood, is disclosed in U.S. Pat. No. 4,159,114 issued Jun. 26, 1979 to Ardell et al. The drawback of the hollow core proposed by Ardell is described in this document in column 4, line 37 that states: “the laminated construction of FIG. 13 (with a hollow core) tends to be very strong and light-weight but is also extremely expensive to produce”. This high production cost could be due to the fact that creating such an axial hollow core in a hockey stick handle, requires a complicated technology with several production steps.
A similar development, described in Canadian Patent No. 1,180,728 issued Jan. 8 1985 to Michaud, proposes a hollow central cavity partially surrounded with wood. FIG. 2 of this document illustrates a hollow inner shaft portion extending to reach the surface of two layers of fibreglass reinforcement material. As it can be seen in this figure, the hollow section between the wider faces of the body extends to reach the two large opposite sides reinforcements, therefore resulting in sections where the reinforcement alone contributes to the stiffness of the shaft. Hence, it reduces the stiffness of the shaft in the plane of maximum bending of the shaft. Furthermore, it makes the positioning process of the two elongated pieces of wood, between the reinforcing strips, difficult to control, thereby increasing the cost of manufacture of the sticks.
In an attempt to obtain a strong, stiff hockey shaft with reduced weight, hollow shafts of aluminum, composite, hybrids of aluminum and composite, have been developed. These developments have been relatively effective in improving stiffness and strength but have resulted in increasingly expensive hockey sticks.